Long-term therapy with elamipretide normalizes sirtuin-3 protein levels in isolated mitochondria of left ventricular myocardium of dogs with chronic heart failure
Gupta RC, Singh-Gupta V, Castle K, Sabbah HN. Long-term therapy with elamipretide normalizes sirtuin-3 protein levels in isolated mitochondria of left ventricular myocardium of dogs with chronic heart failure. J Am Coll Cardiol. 2018;71(11)
J Am Coll Cardiol
Background: Sirtuins are a highly conserved family ofhistone/protein deacetylases. In mammalian cells, seven sirtuins (SIRT1-7) modulate distinct metabolic and stress-response pathways, with SIRT3 having been most extensively investigated in the cardiovascular system and is mainly located in the mitochondria. SIRT3 is involved in the regulation of energy production, oxidative stress, and cell death/survival. In the heart, impaired activity of SIRT3 has been shown to promote cardiac hypertrophy, mitochondrial (MITO) dysfunction, excessive production of reactive oxygen species (ROS) and opening of mitochondria permeability transition pores (mPTP) leading to progressive heart failure(HF). We previously showed that elamipretide (ELAM), a novel MITO-targeting tetrapeptide, improves function and rate of ATP synthesis and reduces ROS production in LV ofdogs with coronary microembolization-induced HF. Objective: This study tested the hypothesis that reduced SIRT3 protein levels in MITO of LV myocardium of dogs withHF are normalized following chronic therapy with ELAM. Methods: Mitochondria were isolated from LV tissue of 14 dogs with microembolization-induced HF (LV EF∼30%) randomized to 3 months therapy with subcutaneous injections of ELAM (0.5 mg/kg once daily, n=7) or saline (Control, n=7) and from 6 normal (NL) dogs for comparison. Protein levels of SIRT3 and porin, an internal MITO proteinloading control, were determined in MITO fractions by Western blotting coupled with chemiluminiscence, and band intensity was quantifed in densitometric units (du). Results: MITO porin levels were unchanged among the 3 study groups. Protein level of SIRT3 was 1.27 ± 0.09 du inNL, decreased to 0.48 ± 0.05 du in HF-CON (p<0.05 vs. NL) and was normalized following chronic therapy with ELAM (0.98 ± 0.08 du, p<0.05 vs. HF-CON). Conclusion: MITO SIRT3 protein levels are markedly reduced in LV myocardium ofdogs with HF. Chronic therapy with ELAM restores SIRT3 expression to near physiologic levels. These findings provide support for the observations of improved MITO function, reduced cytosolic cytochrome C levels and reduced ROS formation in LV myocardium of dogs with HF treated long-term with ELAM.